The phrase, "Time flies when you're having fun," is often used when one has become absorbed in an activity and lost track of time. I'm looking for a word to describe something that has a tendency to cause someone to lose track of time. I want a word that can be used similarly to something like:
It is a very time-consuming activity.
However, I do not want the word to imply the activity necessitates a large amount of time. Rather, it should imply that the activity is absorbing enough that one spends a large amount of time doing it, without noticing if it's been a long time. I feel as if I know the word I am looking for, it is simply on the tip of my tongue and just out of reach. I'm sorry if my examples and descriptions make little sense. Any help is appreciated though.